The Hard Facts About Fracking

Natural gas doesn't run our lives: As a fossil fuel used to generate electricity, it's in a distant second place behind coal. But with new domestic gas sources—much of it made available thanks to hydraulic fracturing—that all could change, along with (someday) the way you cook your food, heat your home or even drive your car. Here's a look at the facts behind this controversial new way to get to U.S. gas.

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There's a wealth of natural gas trapped underground—but what depths do we have to plumb to extract it? More and more, oil and gas companies are opting for fracking, or hydraulic fracturing: injecting a mixture of sand, water and chemicals into dense rock layers and shale, creating cracks that allow natural gas trapped inside to flow to the earth's surface. Once an also-ran in fossil-fuel prospecting, fracking now figures heavily into the future of U.S. energy production. ExxonMobil recently spent $41 billion to buy shale-gas company XTO Energy; it was the largest single acquisition by ExxonMobil in a decade. ICF Consulting, a Virginia-based energy and environmental consulting firm, projects that unconventional natural gas extraction methods, including fracking, will increase from 42 percent of U.S. gas production in 2007 to 64 percent in 2020. The natural gas industry supplies about 3 million jobs and adds more than $385 billion to the U.S. economy, according to the American Petroleum Institute (API). The trade group says that if hydraulic fracturing were eliminated, natural gas production in the U.S. would fall 57 percent by 2018.

However, fracking has prompted concerns about safety and environmental impact. Last month, the New York State Assembly passed a moratorium on new fracking operations in the state until May 2011, presumably to allow officials to further evaluate the technique. Other states are also wrestling with fracking regulation, balancing economic and environmental interests—and often dealing with controversy. Here, a quick look at the questions at the center of the debate.

How much natural gas comes from fracking in the U.S.?

Pumping slurry into the earth to open up cracks allows companies to harvest natural gas deposits they wouldn't otherwise be able to access. According to a 2009 study by the Potential Gas Committee, which tracks gas supplies, natural gas reserves in the U.S. jumped 35 percent from 2006 to 2008—due in part to increased use of hydraulic fracturing techniques. "Increasingly, the natural gas in this country comes from* tight sands and shale," says Sara Banaszak, an economist at the American Petroleum Institute, which represents hundreds of gas and oil companies. "Before we figured out that we could use [fracking] techniques, the forecast was that we would be importing more and more natural gas." The National Petroleum Council claims that 60 to 80 percent of new U.S. natural gas wells will need hydraulic fracturing to stay productive.

How much natural gas does the U.S. consume? Is most of it domestic or foreign?

In 2009, the U.S. imported about 12 percent of the natural gas it consumed, according to the U.S. Energy Information Administration (EIA)—the lowest percentage since the 1990s. During that year, natural gas supplied about 23 percent of the total electric power generated in the U.S.; coal, the clear leader, supplied 44 percent, while nuclear, the runner-up to natural gas, supplied only 20 percent.

Where are the natural gas fields in the U.S.?

While natural gas fields are scattered all over the country, some of the fields ripest for fracking are the Marcellus Shale field, which covers parts of Ohio, Pennsylvania, West Virginia and New York; the Antrim Shale field in Michigan; and the Barnett Shale field in the Fort Worth region of Texas.

Is natural gas—even from fracking—cleaner than other fossil fuels?

Natural gas is often called a clean-burning fuel because it generates only about half as much greenhouse gas as coal, according to the Environmental Protection Agency (EPA). Backers therefore contend that increased use of fracking for natural gas could indirectly benefit the atmosphere. But Cornell University ecology and environmental biology professor Robert Howarth has disputed this point. Methane—a greenhouse gas about 20 times more effective at trapping heat than carbon dioxide—can leak during hydraulic fracturing, and factors such as this, Howarth argues, may give natural gas a larger greenhouse gas footprint than coal.

Are the fluids used in fracking toxic?

Often, companies that perform fracking operations don't publicly reveal what compounds they use to facilitate the gas extraction process. (Halliburton may prove an exception to the rule; it has agreed to give the government data about the fracking chemicals it uses by January 2011.) When Farnham & Associates, an environmental engineering firm, tested a well near a hydraulic fracturing zone in Pennsylvania, it found a range of contaminants in the water, including ethylene glycol and toluene, both of which can be toxic to humans. They appear on a Pennsylvania Department of Environmental Protection list of compounds known to be used in hydraulic fracturing, but Cabot Oil and Gas, the company that conducted the drilling, claimed it had not used the chemicals.

What impact does fracking have on drinking water?

Some people living near fracking sites have reported abnormalities in their tap water, including dark-colored grease, sediments and floating debris. The EPA has revealed plans to conduct a large-scale study to look into the problem further. "There are serious concerns about whether the process of hydraulic fracturing impacts drinking water. Further study is warranted," the agency announced in a statement released earlier this year. The investigation is slated to begin in January 2011.

Is it true that fracking can cause earthquakes?

Because fluid injection changes seismic dynamics underground, fracking has the potential to set off minor quakes. A study in the journal Earthquake Science pinpointed the location of more than 150 microearthquakes caused by hydraulic fracturing, and the Dallas–Fort Worth region of Texas—a fracking hub—experienced 11 mini quakes in less than a month between November and December 2008. Granted, such mini man-made earthquakes are harmless, but some critics are concerned that there may be a small risk of more hazardous quakes—such as a 5.5-magnitude quake outside of Denver, Colo., in 1967, that resulted after chemical waste was injected deep into the ground for several years as a disposal method. (An SMU study suggests the quakes may have been triggered by the underground wastewater fluid disposal that accompanied the hydraulic fracturing.)

* Earlier, this read, "Increasingly, the natural gas in this country comes from geologies that are not sedimentary—they tend to be tight sands and shale," but as one commenter pointed out, shale is a form of sedimentary rock.